Docking and Drilling Stations for Running Self-Standing Risers and Conducting Drilling, Production and Storage Operations

ABSTRACT

A sea vessel exploration and production system is provided, wherein the system includes a drilling station formed from at least one section of a first sea vessel hull; and a docking station, which is also formed from at least one section of a second sea vessel hull. A mooring system suitable for connecting the drilling station to the docking station is also provided. Means for anchoring the vessels to the seafloor, and for attaching them to turret buoys, are also considered. Various exploration and production packages, as well as equipment required to deploy and control a self-standing riser system in either deep or shallow waters, are also described.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of prior U.S. ProvisionalApplication No. 61/003,657, filed Nov. 19, 2007.

FIELD OF THE INVENTION

The present invention relates generally to offshore facilities used inconnection with the exploration and production of oil and gas, and in aparticular though non-limiting embodiment, to a docking and drillingvessel system suitable for deploying self-standing risers and conductingoil and gas drilling, production and storage operations.

BACKGROUND OF THE INVENTION

Offshore drilling is quickly becoming the prevalent method of exploringand producing oil and gas, especially in Western countries where landoperations are frequently inhibited by environmental concerns. There is,however, a serious shortfall of offshore drilling units called MobileOffshore Drilling Units, or MODUs. The relative unavailability of MODUshas resulted in significant delays in many drilling projects.Consequently, the cost of obtaining either a new or existing MODU for anexploration and production operation has dramatically increased over thepast decade.

As will be readily appreciated by those of skill in the art, MODUs areutilized during the early testing phase required to evaluate oil, gas,and other hydrocarbon discoveries. However, due to the lack of floatingproduction facilities and the high cost of MODUs, early testing isseldom accomplished, which often results in unnecessary delays andinaccurate predictions of economic assessments, project developmentschedules, etc. Moreover, procurement of offshore production and storagefacilities required to operate offshore projects in a timely manner canbe quite difficult. In extreme circumstances or in especially remoteregions, the lag time between hydrocarbon discovery and the productionphase can reach 10 years or more.

Meanwhile, self-standing riser assemblies supported by buoy devices arebecoming a more common method of performing oil and gas exploration andproduction related activities. Compared to the large scale riserassemblies typically serviced by MODUs, the self-standing riser providesfor lighter and less expensive riser tubulars (e.g., drilling pipe,stack casing, etc.). Self-standing risers also admit to the use oflighter blowout preventers, such as those used by land drilling rigs.

Moreover, the top buoy of a self-standing riser system can be positionednear the surface of the water in which it is disposed (for example, lessthan around 100 ft. below surface level), allowing for efficientdrilling in even shallow waters. Furthermore, where riser systems aretensioned and controlled with associated buoyancy chambers, buoy-basedsystems can be used successfully in much deeper waters.

However, as those of skill in the art have learned in the field,buoy-based systems utilizing general purpose vessels for riser andbuoyancy chamber deployment are deficient in that large-scale operations(e.g., deployment in very deep or turbulent waters, or projectsinvolving multiple combinations of riser strings and buoyancy chambers,etc.) are very difficult to control, and thus installation, operationand maintenance of the resulting system is significantly impaired.

There is, therefore, a need for a custom vessel that admits to efficientdeployment of large-scale riser systems in a manner similar to themanner of a MODU even when a MODU is not available.

SUMMARY OF THE INVENTION

A sea vessel exploration and production system is provided, wherein thesystem includes a drilling station formed from at least one section of afirst sea vessel hull; and a docking station, which is also formed fromat least one section of a second sea vessel hull. A mooring systemsuitable for connecting the drilling station to the docking station isalso provided. Means for anchoring the vessels to the seafloor, and forattaching them to turret buoys, are also considered. Various explorationand production packages, as well as equipment required to deploy andcontrol a self-standing riser system in either deep or shallow waters,are also described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an overhead view of a docking and drilling station mooredend-to-end, according to example embodiments.

FIG. 1B is a side view of a docking and drilling station mooredend-to-end, according to example embodiments.

FIG. 2 is a schematic diagram of an anchored drilling station anddocking station operating a self-standing riser assembly, according toexample embodiments.

FIG. 3 illustrates a sequence of steps for mooring a docking station anda drilling station using an end-to-end method, according to exampleembodiments.

FIG. 4 illustrates a sequence of steps for mooring a docking station anda drilling station using a side-by-side method, according to exampleembodiments.

FIG. 5 illustrates a sequence of steps for mooring a docking station anda drilling station to a turret buoy anchoring assembly, according toexample embodiments.

FIG. 6 is a schematic diagram of an alternative docking station withside-by-side docking to a docking station, according to exampleembodiments.

FIG. 7 is a schematic diagram of alternative docking station mooringschemes for varying current conditions, according to exampleembodiments.

FIG. 8 is a schematic diagram of a docking station or a drilling stationattached to a turret buoy, according to example embodiments.

DETAILED DESCRIPTION

The description that follows includes exemplary systems, methods, andtechniques that embody various aspects of the presently inventivesubject matter. However, it will be readily understood by those of skillin the art that the disclosed embodiments may be practiced without oneor more of these specific details. In other instances, well-knownmanufacturing equipment, protocols, structures and techniques have notbeen shown in detail in order to avoid obfuscation in the description.

Referring now to the example embodiment illustrated in FIG. 1A, anoverhead view of a docking station 6 and a drilling station 8 aredepicted as being moored together in an end-to-end manner. Theembodiment of the drilling station shown in FIG. 1B comprises crewquarters and an operations office; a drilling rig; a void space designedfor housing and deploying various buoyancy devices; a helipad; a moonpool; a plurality of anchor lines used to anchor the system to anassociated seabed; and mooring lines configured to moor said drillingstation and said docking station together. The example embodiment of thedocking station further comprises modular production, testing andinjection facilities; a plurality of anchor lines; and mooring linesconfigured to mate with the mooring assembly of the drilling station. Aself-standing riser disposed in mechanical communication with one ormore buoyancy devices is also provided.

In the embodiment depicted in FIG. 1A, the docking station 6 anddrilling station 8 are moored together using mooring lines in such amanner that both portions of the combined vessel are able to properlyperform offshore drilling operations. In alternative embodiments,various other devices can be used to secure the mooring system, forexample, clamps, rods, latches, locks and other mechanical devices;strong magnets and electrical control systems; vacuum systems, etc.

Although not illustrated in FIG. 1, typical embodiments of the dockingand drilling stations further comprise a plurality of oil and gasrelated drilling, production and exploration equipment. For example, amodified land or platform drilling rig installed on the drilling stationcan be used to operate a self standing riser while maintainingfunctional stability and efficient operational continuity. Similarequipment disposed within or upon the drilling station 8 enablesstorage, deployment, lifting, and retrieval operations, as well asstorage of additional riser and one more buoyancy devices should they berequired during drilling operations.

In further embodiments, hydrocarbons such as oil, gas, liquid naturalgas, etc., encountered during the drilling process are separated,treated and stored either onboard or within docking station 6. In stillfurther embodiments, docking station 6 further comprises modularproduction facilities and storage space that can be used for testingoperations or as a facility to separate oil, gas, water, etc. Otherembodiments of the docking station 6 comprise one or more of a flareboom used to bleed off gas and fluid pressure; oil, water and gasseparators; and storage facilities used to store crude and previouslytreated oil and gas. In further embodiments still, water and gasinjection equipment used to re-inject wells and the mechanical equipmentrequired to facilitate such operations are also included.

Since the drilling station does not necessarily have to supportdeployment of conventional riser and buoyancy chamber systems, it canutilize a typical land or platform drilling rig modified to endureextreme sea and weather conditions. The embodiment depicted in FIG. 2,for example, illustrates an anchored drilling station and dockingstation operating in tandem to support and control a self-standing risersystem equipped with an associated buoyancy device. The drilling stationof FIG. 2 further comprises a void space suitable for the storage andhandling of buoyancy devices, as well as a hoisting system andretractable guide rails that assist in guiding the buoyancy devicesbelow the hull of drilling station.

In various other embodiments, the drilling station depicted in FIG. 2allows the drilling rig to hoist, lower and otherwise handle selfstanding riser, casing, drilling pipe, etc., passed through the moonpool. One specific example embodiment permits self standing risertubulars to be lowered into the water until a desired length is obtainedand the required quantity of buoyancy devices are in place. Although notdepicted, those of skill in the art will appreciate that furtherembodiments of the drilling station are equipped to deploy, store andhandle most other types of routine or custom fit offshore drillingequipment, such as shear rams, ball valves, blowout preventers andhoists therefor.

Following installation of the self standing riser, the drilling stationcan commence drilling, completion, testing and workover operations, etc.As operations continue, some portions of the system can be removed sothat the drilling station can be utilized in other types of operations.In further embodiments, the drilling station is utilized to drill a holein a seabed so as to permit installation of a wellhead and associatedcasing. In still further embodiments, the drilling station is used toremove and store the riser assemblies, as well as attendant buoyancydevices and other offshore drilling equipment.

In some example embodiments, the described installation and removalprocess is applied to wellheads created by others and abandoned. Suchprojects would typically utilize cranes, hoists, winches, etc.,operating in mechanical communication with the drilling station in orderto perform installation and removal of existing riser assemblies,wellheads, production trees and blowout preventers.

In some embodiments, the void space formed to store and handle buoyancydevices further comprises a moveable floor, tracks, a gantry, etc., thattransports buoyancy devices to a desired location (e.g., near the moonpool) to be joined with a self standing riser assembly stack. Variousembodiments of the moon pool further comprise retractable guide railsthat assist in guiding and delivering the buoyancy devices down belowthe hull to a deployment station.

End-to-End and Side-to-Side Mooring of the Docking and Drilling Stations

FIGS. 3 and 4 depict an embodiment of the docking station and thedrilling station moored together using end-to-end and side-to-sidemooring methods, respectively. In the example embodiment illustrated inStep 1 of both FIGS. 3 and 4, docking station is towed by a towingvessel toward anchor lines preinstalled by workboats, anchor handlingvessels, etc. Towing of the docking and drilling stations can of coursebe facilitated by any vessel capable of towing another vessel ofappropriate size, such as a work boat, a tug, etc.

Step 2 depicts various transportation vessels (e.g., workboats, towingvessels, etc.) transporting a plurality of anchor lines to fasteningmembers disposed in communication with the docking station. Someembodiments of the fastening members assist in adding tension to theanchor lines, and slowly moving the docking station toward desired sitecoordinates.

In the end-to-end embodiment shown in FIG. 3, the anchor lines areaffixed to fastening members positioned on all sides of the dockingstation. Note, however, that the anchor lines would typically be affixedto fastening members on a particular side of the docking station in theside-to-side method depicted in Step 2 of FIG. 4. Such embodiments ofside-to-side mooring help maintain proper lateral spacing and controlledefficient movement as the drilling station and docking station arejoined. In further embodiments, the drilling station 8 is transported towithin a close proximity of the docking station 6 during Step 2, and aplurality of anchor lines are thereafter affixed to fastening members ofthe drilling station in order to secure the system in a desired dynamicequilibrium.

Step 3 illustrates the drilling station as disposed in stable operativecommunication with the docking station. Various known attachment means,such as mooring lines, as well as any new or custom designed fastenersor the like can be used to facilitate stable and reliable operations. Inthe embodiment depicted in FIG. 3, the drilling station and the dockingstation are mutually joined and operated in a back-to-back or end-to-endmanner, whereas in the embodiment illustrated in FIG. 4, the drillingstation and the docking station are joined in a side-to-side manner.Either manner will, if configured correctly, permit the drilling stationto drill, deploy casing, deploy self standing riser tubulars, etc. Insome embodiments, the drilling station is configured to position itselfover an existing self standing riser system in order to perform workoveroperations, well completions, and other common drilling operations.

In the embodiment illustrated in Step 4 of FIGS. 3 and 4, the drillingstation is disconnected from the docking station and towed away. In atypical example embodiment, anchoring lines previously used to anchorthe drilling station in place are attached to the remaining dockingstation, thereby resulting in a spread mooring configuration suitablefor receiving a new vessel. In some embodiments, the docking station isthen used as a testing or production vessel to process and separate oil,gas and water, etc. In further embodiments, the docking station providefacilities to inject water and gas back into well(s), power to operateelectric submersible pumps, or lifting support to aid with otherproduction methods.

Step 5 depicts an embodiment of the mooring sequence in which an oiltanker is joined in communication with the docking station. Aspreviously discussed, example embodiments may comprise a wide variety ofattachment methods and means, such as mooring, docking, fastening, etc.In one example embodiment, the docking station then utilizes pipes,tubulars, hoses, etc., to transfer oil, gas or other stored fluids toand from the tanker.

End-to-End Mooring Using a Turret Buoy

FIG. 5 depicts an embodiment of a turret buoy mooring process thatallows the drilling station and the docking station to cooperate in asynchronized manner even in very poor weather conditions, such as strongwinds, rough currents, etc. In the embodiment illustrated in Step 1 ofFIG. 5, conventional mooring lines and anchors are affixed to a turretbuoy as known in the art. Embodiments of the drilling station aresubsequently towed to the turret buoy, as illustrated in Step 2. In theembodiment depicted in Step 3, a plurality of towing vessels positionthe drilling station in relatively close proximity to the turret buoy,where the drilling station and the turret buoy are mutually joined. InSteps 4 and 5, the docking station is similarly joined to the system inaccord with the principles previously discussed above. In one specificembodiment, the drilling station is also capable of performing amultitude of other offshore drilling functions, including deployment andoperation of drilling equipment; the drilling of holes on the seabed andinstallation of casing; deployment and operation of self-standing riser,etc.

In the embodiments illustrated in Step 5 and Step 6, the docking stationis moved to a location and attached in communication with the turretbuoy after completion of operations by the drilling station. In furtherembodiments, the drilling station is then removed from the turret buoyto allow for attachment of the docking station so that testing andproduction can commence.

Side-by-Side Mooring Using a Spread Mooring System

Referring now to the example embodiment depicted in FIG. 6, the dockingstation and drilling station are joined using a side-by-side mooringsystem. Various embodiments of the drilling station are affixed to thedocking station using a system of attachment mechanisms, such asmooring, docking, fastening devices, etc., which lend support andprovide rigid separation in the lateral direction while still allowingmutual vertical movement. In one embodiment, conventional mooring withanchor lines can secure the drilling station and docking station inproximity of a self-standing riser. Several embodiments of side-by-sidemooring utilize hydraulically compensated cylinders to maintain constantlateral distance and compensate for wave and swell actions. For example,embodiments using a hydraulically compensated cylinder can maintainseparation forces while dampening related transient forces caused bywave and swell movement.

End-to-End and Side-by-Side Mooring of the Drilling Station and DockingStation Using the Turret Moored Buoy

Referring now to the example embodiment in FIG. 7, side-by-side andend-to-end mooring configurations of the drilling station and dockingstation attached in communication with a turret buoy is illustrated. Insome embodiments, the turret buoy is utilized for situations where aparticular area of the water has significantly varying or conflictingcurrents. In further embodiments, the turret buoy is designed to beattached to a self-standing riser, while relative positioning of thedrilling station and docking station is maintained. According to stillfurther embodiments, the design of the turret buoy varies depending onthe dimensions of the docking or drilling stations, or in conformitywith the dimensions of the moon pool.

In some embodiments, the drilling station and the docking station attachto the turret buoy using mechanical or hydraulic couplers or otherfastening devices known in the art. In the embodiment illustrated inFIG. 8, the turret buoy allows for a 360 degree rotation of theparticular station with which it is disposed. For example, the dockingstation can rotate 360 degrees once it is attached to the turret buoy.

In some example embodiments utilizing a turret buoy, the drillingstation is moored first, and used to perform one or more of drilling,deployment, workover, completion, testing, etc., operations. In otherembodiments, the docking station is moored to the drilling station, andused to conduct one or more of the aforementioned operations, asdepicted in FIG. 8. Once the work of drilling station is concluded, itis detached from the turret buoy while the docking station remainsbehind for continued operations.

The foregoing specification is provided for illustrative purposes only,and is not intended to describe all possible aspects of the presentinvention. Moreover, while the invention has been shown and described indetail with respect to several exemplary embodiments, those of ordinaryskill in the art will appreciate that minor changes to the description,and various other modifications, omissions and additions may also bemade without departing from the spirit or scope thereof.

1. A sea vessel exploration and production system, said systemcomprising: a drilling station, wherein said drilling station furthercomprises at least one section of a first sea vessel hull; and a dockingstation, wherein said docking station further comprises at least onesection of a second sea vessel hull.
 2. The sea vessel exploration andproduction system of claim 1, further comprising a mooring systemsuitable for mooring said drilling station in communication with saiddocking station.
 3. The sea vessel exploration and production system ofclaim 1, further comprising one or more anchor lines configured toposition and stabilize said drilling station and said docking station.4. The sea vessel exploration and production system of claim 1, furthercomprising a turret buoy system disposed in permissive communicationwith either of said drilling station and said docking station.
 5. Thesea vessel exploration and production system of claim 1, wherein saiddrilling station further comprises a moon pool.
 6. The sea vesselexploration and production system of claim 1, wherein at least one ofsaid drilling station and said docking station further comprises ahydrocarbon testing unit.
 7. The sea vessel exploration and productionsystem of claim 1, wherein at least one of said drilling station andsaid docking station further comprises a hydrocarbon separation unit. 8.The sea vessel exploration and production system of claim 1, wherein atleast one of said drilling station and said docking station furthercomprises a storage unit for storing equipment relating to aself-standing riser system.
 9. The sea vessel exploration and productionsystem of claim 8, wherein said equipment relating to a self-standingriser system further comprises additional lengths of riser tubulars. 10.The sea vessel exploration and production system of claim 8, whereinsaid equipment relating to a self-standing riser system furthercomprises one or more buoyancy chambers.